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Low-tech greenhouse could hold promise of year-round growth

Imagine being able to live in Colorado but garden as if you were living in north Texas.

Enter the world of farming with high tunnels, which some Colorado producers are using to extend their growing season to year-round.

That’s no small feat for a state offering 120 frost-free days on the Front Range, and even fewer in the mountains.

High tunnels also are called hoop houses, and are basically low-tech greenhouses making use of no supplemental heating or cooling outside of natural ventilation, said Frank Stonaker, director of Colorado State University’s Specialty Crops Program.

He and graduate assistant Dan Goldhamer will be giving a presentation near Silt today on making use of high tunnels in winter production of organic vegetables such as carrots, spinach, radishes and lettuce. The event is at Divide Creek Farm.

The farm is in its second year of winter production, said Clara Coleman, who owns the farm with Robbie George. But her father, organic gardening pioneer and author Eliot Coleman, has been making use of high tunnels for 40 years in Maine.

High tunnels consist of a durable greenhouse plastic stretched over curved frames. They get their name because they’re high enough to walk in and sometimes even drive a tractor into, Stonaker said.

He said they tend to cost perhaps a tenth or less as much as a climate-controlled greenhouse. When combined with lightweight fabrics that are draped on top of the plants, they can produce temperatures that might be above freezing even when it’s minus 20 degrees outside, Stonaker said.

The result can be changing the growing climate inside the tunnels by two climate zones, he said. That could be enough to help growers offer their product, and keep employees, year-round, Stonaker hopes.

Divide Creek Farm is one of several around the state participating with CSU in research in the use of high tunnels.

Other western Colorado participants include Daphne Yannakakis and Don Lareau, owners of Zephyros Farm and Garden in Paonia, and Melissa Betrone of Dolores.

The high tunnels let Coleman sell greens in winter markets, along with carrots that turn sweet when their starches turn to sugars in the cold but not freezing winter ground.

She’s doing that without having to spend a lot heating a greenhouse “even in the mountains, the Rocky Mountains of Colorado, where we do get extreme temperatures and most people think it would be impossible to do what we’re doing,” she said.